1. Field of the Invention
The present invention relates to a laminated ceramic electronic component typified by a laminated ceramic capacitor, for example, and more particularly, relates to a laminated ceramic electronic component including an internal electrode containing Al as its main constituent.
2. Description of the Related Art
With reference to FIG. 1, a laminated ceramic capacitor 1 will be described first which is a typical example of a laminated ceramic electronic component.
The laminated ceramic capacitor 1 includes a laminate 2 composed of a plurality of stacked dielectric ceramic layers 3 and a plurality of internal electrodes 4 and 5 formed along specific interfaces between the dielectric ceramic layers 3.
First and second external electrodes 8 and 9 are formed in different positions from each other on the outer surface of the laminate 2. The laminated ceramic capacitor 1 shown in FIG. 1 has the first and second external electrodes 8 and 9 formed on respective end surfaces 6 and 7 of the laminate 2 opposed to each other, respectively. The internal electrodes 4 and 5 include a plurality of first internal electrodes 4 electrically connected to the first external electrode 8 and a plurality of second internal electrodes 5 electrically connected to the second external electrode 9, and these first and second internal electrodes 4 and 5 are alternately arranged with respect to the staking direction.
Since reduction in size is required, in particular, for laminated ceramic capacitors, an approach in which green sheets of a dielectric ceramic and internal electrode layers are stacked and then fired simultaneously is employed in the production process. In recent years, for the purpose of cost reduction, a base metal such as Ni has been used for internal electrodes of laminated ceramic capacitors.
However, since Ni is very likely to be oxidized in a co-firing process with the ceramic, it has been necessary to bring the atmosphere for firing into a reducing atmosphere and precisely control the temperature condition and the oxygen partial pressure. As a result, the material design is limited significantly. In addition, problems such as delamination and cracks have occurred and are caused by non-uniform stress associated with the co-firing.
Therefore, in order to increase the degree of freedom in the design of laminated ceramic electronic components, it is preferable to study internal electrodes made from a variety of metal materials.
For example, DE 19719174 A1 discloses a laminated ceramic body employing Al as an internal electrode material instead of Ni. However, since the melting point of Al is about 660° C., the ceramic has to be able to be sintered at about 660° C. in terms of the conventional rule of common sense. Thus, the laminated ceramic body has a problem in that the degree of freedom in the design of ceramic materials is limited significantly.
However, the laminated ceramic electronic component disclosed in DE 19719174 A1 has a problem in that the Al internal electrode is made into a spherical shape, resulting in an inability to secure sufficient conductivity, because the firing temperature is 1200° C. which is much higher than the melting point of Al at 660° C.
Furthermore, the laminated ceramic electronic component disclosed in DE 19719174 A1 has a problem in that the Al to define the internal electrodes is changed to an aluminum nitride (AIN), resulting in the inability to secure sufficient conductivity, because the firing atmosphere is a nitrogen atmosphere with an oxygen partial pressure of 10−5 atm.